In many operations involving the movement of a member under pressure-fluid control, there is a requirement or at least a desire, for rapid movement to a precisely defined position. For example, in automatic operation of a valve for controlling pipeline flow, it is desirable to have the control valve move rapidly when there is a substantial deviation from a desired flow characteristic, but it is also desirable that the adjusted setting of the valve be reached with precision, to avoid a cycling operation. In the case of sizable pipeline valves a small movement of the valve can effect a substantial change in the process variable. Accordingly in order to maintain precise control it is necessary to terminate movement immediately upon reaching the control point. However, if the rate of valve movement is high, it is extremely difficult to terminate same with the desired precision. Accordingly, it is desirable to slow the valve during the final increment of movement to facilitate precision termination. Another related problem is encountered in analog control devices. Specifically, when a reversal of direction is dictated, it is necessary for the controlling element to continue in its original direction until flow can be shut off, before it can reverse and commence flow in the opposite direction.